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Investment Securities Investment Securities Text Tags (Details) | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2018 USD ($) | Sep. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Sep. 30, 2018 USD ($)
Schedule of Investments [Line Items] |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions |  | 24 | 35 |
Available-for-sale |  | $ 75,109,000 | $ 79,845,000 |
Percentage Available-for-sale Securities |  | 87.60% |  |
Held-to-maturity |  | $ 10,680,000 | 11,137,000 |
Percentage Held-to-maturity Securities |  | 12.40% |  |
Trading |  | $ 0 |  |
Equity Method Investment, Amount Sold | $ 9,200,000 |  |  |
Proceeds from Sale of Available-for-sale Securities |  | $ 0 |  |
Mortgage-backed securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percentage Available-for-Sale, Continuos Unrealized Loss Position |  | 40.60% |  |
Number of AFS securities in Unrealized Loss Positions, greater than or equal to 12 months |  | 13 |  |
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions |  | 1 |  |
Held-to-maturity |  | $ 9,680,000 | 10,137,000 |
US Government Agency Securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percentage Available-for-Sale, Continuos Unrealized Loss Position |  | 53.70% |  |
Number of AFS securities in Unrealized Loss Positions, greater than or equal to 12 months |  | 3 |  |
Corporate Bonds |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Number of AFS securities in Unrealized Loss Positions, greater than or equal to 12 months |  | 3 |  |
Held-to-maturity |  | $ 1,000,000 | $ 1,000,000 |
Accounting Standards Update 2016-01 |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Cumulative Effect of New Accounting Principle |  |  |  | $ 0
Accounting Standards Update 2016-01 | Accumulated Deficit |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Cumulative Effect of New Accounting Principle |  |  |  | $ (721,000)

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